1. Field of the Invention
This invention pertains generally to electro-optic devices, and more particularly to an in-line polymeric fiber construct suitable for fabrication of electro-optic devices such as high speed modulators, tunable wavelength filters, and space division switches.
2. Description of the Background Art
Much of the external optical modulator technology in use today is based on integrated optic lithium niobate devices. An example is a lithium niobate amplitude modulator which is typically based on a Mach-Zehnder interferometer structure, and which has demonstrated half-wave voltages of &lt;5 V at frequencies of &lt;5 GHz. However, despite further development over many years, lithium niobate integrated optic modulators exhibit excessive insertion loss, are expensive and bulky, are not mechanically rugged, and exhibit high intermodulation distortion (IMD). Further, due to the fundamental mismatch in the phase velocity of radio-frequency and optical waves in lithium niobate, such modulators tend to require excessive drive power at high frequencies.
Improved electro-optic (EO) materials, however, are gaining popularity for advanced photonic devices such as efficient high speed modulators, rapidly tunable filters for wavelength division multiplexing (WDM), and low switching voltage directional couplers for space division switching. Due to their cost and fabrication advantages, EO polymers are leading candidate materials for these applications. However, for EO polymers to be used as a replacement for lithium niobate in standard integrated optics devices, it is necessary for the EO polymers to be stable for brief exposure to 250.degree. C., to have an EO coefficient of greater than 30 pm/V, and to have a loss of less than 1 dB/cm. While there has been significant progress on improving the temperature stability of EO polymer materials, there is no presently available EO polymer material that simultaneously satisfies the high EO coefficient and low loss requirement of such devices.
Conventional polymeric and lithium niobate based devices that take advantage of evanescent coupling have been developed to alleviate problems associated with the pigtailing of integrated optics devices. Because such devices rely on evanescent coupling to the electro-optic material, rather than propagation through it, insertion losses are greatly reduced and a mechanically rugged, self-pigtailed device can be fabricated. However, assembly has been complicated due to the difficulties of working with devices with attached fibers, and development of high speed devices has been limited.
Accordingly, there is a need for a device technology that permits the use of EO polymers as an alternative to lithium niobate notwithstanding the current deficiencies in EO polymers, and which provides a more facile path for near-term insertion of EO polymers into applications such as high speed modulators, tunable wavelength filters, and space division switches. The present invention satisfies those needs, as well as others, and provides for a new region of parameter space for EO polymer materials development.